MySQL查询对具有组值的行数进行计数

Question

I have a list of stock ordered by a number of users. i need to know how many of the stock are labeled priority = 'Y' and 'N'

SELECT
glidemedia.glide_outlet.run,
glidemedia.glide_stock.title,
glidemedia.glide_stock.stockID,
glidemedia.glide_stock.titleID,
glidemedia.glide_schedule_entry.priorityItem,
count(glidemedia.glide_schedule_entry.stockID) as stockCount,
count(glidemedia.glide_schedule_entry.priorityItem = 'Y') as priorityItemYes,
count(glidemedia.glide_schedule_entry.priorityItem = 'N') as priorityItemNo
FROM
glidemedia.glide_outlet
INNER JOIN glidemedia.glide_schedule_entry ON glidemedia.glide_outlet.outletID = glidemedia.glide_schedule_entry.outletID
INNER JOIN glidemedia.glide_stock ON glidemedia.glide_schedule_entry.stockID = glidemedia.glide_stock.stockID
WHERE
glidemedia.glide_outlet.run = 109
GROUP BY
glidemedia.glide_schedule_entry.stockID

Answer 1

Change

count(glidemedia.glide_schedule_entry.priorityItem = 'Y') as priorityItemYes,
count(glidemedia.glide_schedule_entry.priorityItem = 'N') as priorityItemNo

to

sum(glidemedia.glide_schedule_entry.priorityItem = 'Y') as priorityItemYes,
sum(glidemedia.glide_schedule_entry.priorityItem = 'N') as priorityItemNo

For ANSI standard its

sum( 
 case when glidemedia.glide_schedule_entry.priorityItem = 'Y' then 1 else 0 end
) as priorityItemYes

UPDATE Why sum() instead of count() , the reason is you are not counting the number of rows rather you are counting the sum/number of times certain column value is appearing using some condition.